Bosch Service

In 1997, Bosch launched the first car-based common rail system onto the market. The market launch for commercial vehicles took place in 1999. The system takes its name from the common high-pressure storage tank (common rail) which supplies all cylinders with fuel. In conventional diesel injection systems, the fuel pressure must be generated separately for each injection. In the common rail system, however, pressure generation and injection are separate, so that the fuel is permanently available at the pressure necessary for injection.

The common rail system

Common rail systems feature a modular structure. The high-pressure pump, injectors, rail and electronic control unit all belong to one system. Bosch offers common rail systems for various medium and heavy-duty applications in on-and-off-highway use. They attain peak injection pressures of up to 2,500 bar – even in the part load range. This guarantees low fuel consumption with correspondingly reduced CO₂ emissions and enables exhaust gas recirculation to reduce nitrogen oxides (NOx). In doing so, Bosch common rail systems make an important contribution to meeting the strictest emissions targets for commercial vehicles, such as Euro 6 or US10.

Operation

In conventional diesel injection systems, the fuel pressure must be generated separately for each injection. In the common rail system, however, pressure generation and injection are separate, so that the fuel is permanently available at the pressure necessary for injection. Pressure generation takes place in the high-pressure pump. This compresses the fuel and carries it via a high-pressure pipe into the rail intake, which serves as a common high-pressure storage tank for all injectors – hence the name "common rail" . From here, the fuel is distributed to the individual injectors, which inject it into the combustion chamber of the cylinder.

Benefits

Clean and highly-efficient fuel injection through extremely short injection intervals and multiple injections

High engine performance and smooth running with low consumption and emissions

Can be installed in most commercial vehicles thanks to modular design

High-pressure pumps

The high-pressure pump compresses the fuel and makes it available in the quantity required. To do so, it permanently feeds fuel into the high-pressure storage tank (rail) and thereby maintains the system pressure. The necessary pressure is already available at lower engine speeds, as the pressure generation is decoupled from the speed. Bosch high-pressure pumps for commercial vehicles are particularly light thanks to their aluminum housing. A mechanical supply pump is already integrated. The sophisticated technology ensures a long service life of up to 15,000 working hours or distances of up to 1.6 million km.

Injectors

Bosch offers particularly efficient solenoid valve injectors for common rail systems in commercial vehicles. The injectors are installed individually in each engine cylinder and are connected to the rail via a short high-pressure pipe. The Electronic Diesel Control (EDC) is responsible for controlling them. It opens or closes the nozzle needle through the solenoid valve. The Bosch injector concept guarantees a high level of hydraulic efficiency and therefore also lower fuel consumption than conventional solutions.